Boundary lubrication of magnetorheological fluids in PTFE/steel point contacts

This paper is concerned with an experimental investigation of the boundary lubrication properties of magnetorheological (MR) fluids under point sliding contacts between polytetrafluoroethylene (PTFE) and stainless steel tribopairs. The tribological properties of OM, OS, OX, HS, HSI and HQ grades of carbonyl iron based MR fluids were tested using a ball-on-three plates tribometer to ascertain the optimal lubricant. Wear scars on the PTFE sheets were examined by optical microscopy, environmental scanning electron microscopy (ESEM) and energy dispersive X-ray spectroscopy (EDX) for imaging and elemental analysis of the worn surface. The research shows that OS based lubricating MR fluids have the optimal anti-wear and friction reducing properties probably due to the amorphous silica surface coating of the particles. Mechanisms by which MR fluids improve tribological behavior concern particle entrapment and (soft) surface indentation.